In semiconductor processing equipment, a showerhead is often used to distribute process gases across a semiconductor wafer in a desired manner, e.g., in an evenly distributed manner. Such showerheads typically include a plenum that is bounded by a faceplate with a plurality of gas distribution holes that lead to the outside of the showerhead. The faceplate typically faces a wafer reaction area within a semiconductor processing or reaction chamber, and wafers are usually placed beneath the faceplate within the processing chamber, e.g., on a wafer support or pedestal that supports the wafer in a location below the faceplate.